Hi Dee Jay,
We had a similar scenario with my mum a couple of years ago, she was 88, sufferring from vascular dementia, hard of hearing etc.
When her blood tests revealed that she was anaemic the doctors suspected bowel cancer, her GP took me to one side and explained that while he could refer her for all sorts tests such as a barium enema, there was little point doing so because had the doctors located and identified an intestinal tumour, mum was not strong enough to cope with treatment, accordingly why put her through the stress and indignity of the tests?
I don't know if your dad can have a TRUS biopsy while he is on warfarin, the internal bleeding that the TRUS causes is quite bad enough for those of us with thick unthined blood.
There is also quite a bit on the Internet about otherwise fit guys being hospitalised by the TRUS procedure, it seems that in places like Canada and Sweden there is a growing problem with antbotic resistant infections.
My mum died, 18 months later, peacefully in her bed, with her dignity intact, and we never knew whether she had bowel cancer, her death certificate said it was cardiovascular disease that did for her.
:)
Dave